JPH09178115A - Fluidized bed combustion apparatus and its operation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce thermal loss of a flow medium and further reduce powdering and wear of the flow medium. SOLUTION: A fluid medium is transferred from a fluidized bed combustion furnace 6 to a heat recovery cell 23 through a coupling pipe 34, and a lower part of the heat recovery cell 23 and the fluidized bed combustion furnace 6 are connected to each other through piping 29 on which a screw feeder 28 is installed. The fluid medium is robbed of heat by an overheating steam pipe 30 in the heat recovery cell 23, and the cooled fluid medium is transferred into the fluidized bed combustion furnace 6 in a shortest distance without being to the utmost exposed to low temperature fresh air. Hereby, powdering due to heat loss and thermal shock is restricted. Air is blown into the fluidized bed combustion furnace 6 located in the vicinity of the piping 29 from an airation nozzle 31, and the fluid medium is smoothly transferred by reducing resistance at an outlet of the screw feeder 28. Further, the amount of the transfer of the fluid medium from the heat recovery cell 23 into the fluidized bed combustion furnace 6 is secondarily controlled by increasing/decreasing the amount of the airation air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incinerator for municipal waste and the like, and relates to an incinerator for efficiently recovering combustion heat.

[0002]

2. Description of the Related Art When recovering and utilizing the incineration heat of municipal waste as steam, the corrosion of the steam piping that comes into contact with the combustion exhaust gas of the garbage has become a major problem in the equipment. In particular, in a system using a steam turbine, high temperature and high pressure steam conditions are indispensable for improving the thermal efficiency of the plant.However, as the steam conditions become higher and the metal temperature of the steam pipe becomes higher, corrosion increases rapidly. Has become the neck of. Corrosion of pipes with relatively low metal temperatures such as evaporators and economizers can use ordinary low-cost materials, but it is extremely expensive when the fluid (vapor) temperature in the pipes such as superheated steam pipes is high. It is necessary to use different materials.

FIG. 5 shows a system of a refuse incinerator according to the prior art. The air for combustion passes through the air preheater 2 by the forced blower 1 and passes through the pipe 3 to fluidize the in-layer medium blown from the diffuser pipe 5 into the fluidized bed 7 of the fluidized bed combustion furnace 6.

The dust thrown into the fluidized bed combustion furnace 6 reacts with the air blown from the diffuser pipe 5 and burns to heat the fluidized medium, and most of it becomes combustion exhaust gas, and the evaporator 11 and the economizer are used. After passing through 13, the air preheater 2 and the bag filter 14, it is exhausted through the chimney 16 by the induction blower 15. In the evaporator 11, the economizer 13, and the air preheater 2, since the fluid temperature in the heat transfer tube is low, corrosion can be suppressed within an allowable range.

Non-combustible foreign matters such as metal pieces and pebbles are contained in the refuse, which cannot be fluidized and are deposited on the bottom of the fluidized bed combustion furnace 6. The fluid medium is extracted from the bottom of the fluidized bed combustion furnace 6 by the screw feeder 19 and sent to the sieve 20, where coarse incombustibles are separated and discharged to the outside of the system. The fine fluidized medium that has passed through the sieve 20 is returned to the fluidized bed combustion furnace 6 again by the bucket conveyor 22 or an air flow carrier pipe (not shown), and becomes a fluidized medium that forms a fluidized bed.

A heat recovery cell 23 installed in the fluidized bed combustion furnace 6
Air is blown through the air diffuser 25, and the internal fluidization state is controlled by the degree of air blowing. That is, the heat recovery cell 23 can be controlled from the moving bed state to the fluidized bed state by adjusting the amount of air from the air diffuser 25. From the lower part of the heat recovery cell 23, a fluidized medium is extracted through a rotary valve 41 and sent to the fluidized bed combustion furnace 6 by a well-known method such as a bucket conveyor 22 or air flow transportation (not shown).

The fluid medium deficient due to the withdrawal of the fluid medium from the lower side of the heat recovery cell 23 is fed from the fluid furnace 6 to the connecting pipe 3.
4 is compensated by the high temperature fluid medium overflowing into the heat recovery cell 23. This high-temperature fluidized medium comes into contact with the superheated steam pipe 30 to give heat to the superheated steam to lower the temperature, and the heat recovery cell 23
Is moved downward and discharged by the rotary valve 41.

Chlorine gas is contained in the combustion exhaust gas of refuse, which is the main cause of corrosion of heat transfer tubes such as the superheated steam tube 30. In the prior art shown in FIG. 5, a heat recovery cell 23 is provided separately from the fluidized bed combustion furnace 6, and only the high temperature fluidized medium from the fluidized bed combustion furnace 6 of waste is collected in the heat recovery cell 23.
The flue gas containing chlorine gas and the superheated steam pipe 30 are prevented from coming into contact with each other by transferring the exhaust gas to the superheated steam pipe 30 and using it as a heat source of the superheated steam pipe 30.

[0009]

The problems to be solved in the above prior art are as follows. a. Since the fluidized medium is extracted from the heat recovery cell 23 and is conveyed by the bucket conveyor 22 or an air flow conveying pipe (not shown), heat is largely dissipated during the conveyance, and the thermal efficiency of the equipment is lowered. b, the temperature of the fluidized medium carried by the bucket conveyor 22 or the air flow carrying pipe (not shown) is cooled to about several tens of degrees Celsius. The fluidized bed combustion furnace 6 in which this fluidized medium is about 800 ° C.
When returned to the inside, the fluid medium is broken and pulverized by the thermal shock due to the temperature difference. The pulverized fluid medium is discharged to the outside of the fluidized bed combustion furnace 6 along with the gas flow in the furnace,
It cannot be reused as a fluid medium. That is, the conventional technique shown in FIG. 5 has a drawback in that the fluidized medium is greatly pulverized and damaged by thermal shock, and the replenishment amount of the fluidized medium is large.

An object of the present invention is that the heat loss of the fluidized medium when it is conveyed from the heat recovery cell 23 to the fluidized bed combustion furnace 6 in the above-mentioned prior art is large, and that the fluidized medium is pulverized and the amount of wear is large. It is to solve.

In other words, it is an object of the present invention to provide a fluidized bed combustion apparatus and a method for operating the fluidized bed combustion apparatus, in which the heat loss of the fluidized medium is small, and the fluidized material is pulverized and the amount of wear is also reduced.

[0012]

The above object of the present invention is achieved by the following constitution. That is, in a fluidized bed combustion apparatus provided with a heat recovery cell provided with a heat transfer tube for transferring a fluidized medium between the fluidized bed combustion furnace and the fluidized bed combustion furnace in which fluidized air is blown into the fluidized bed combustion furnace. Extract the fluidized medium from the upper part of the combustion furnace, put it in the heat recovery cell, and return the fluidized medium after heat exchange in the heat recovery cell to the lower part of the fluidized bed combustion furnace. In a fluidized bed combustion apparatus provided with a heat recovery cell having a heat transfer tube for transferring a fluidized medium between the fluidized bed combustion furnace and the fluidized bed combustion furnace, which is performed by blowing fluidized air, from the upper part of the fluidized bed combustion furnace. In the fluidized bed combustion apparatus, an extraction pipe for extracting the fluidized medium is provided above the heat recovery cell, and a return pipe for returning the fluidized medium after heat exchange is provided from the lower portion of the heat recovery cell to the lower portion of the fluidized bed combustion furnace.

In the above fluidized bed combustion apparatus or its operating method of the present invention, the fluidized medium of the heat recovery cell is returned to the lower part of the fluidized bed combustion furnace by a screw feeder, and the same level as the fluidized air blowing position of the fluidized bed combustion furnace is used. Return the fluidized medium from the heat recovery cell to the fluidized bed combustion furnace to a lower position or lower the gas inside the fluidized bed combustion furnace, which is the outlet of the screw feeder that connects the heat recovery cell and the fluidized bed combustion furnace. By controlling the amount of the fluid medium transferred from the heat recovery cell to the fluidized bed combustion furnace by blowing it, at the same time promoting the mixing of the fluidized medium transferred from the heat recovery cell to the fluidized bed combustion furnace, the heat recovery cell and the fluidized bed combustion A partition is provided inside the fluidized bed combustion furnace, which is the exit of the screw feeder that connects the furnaces, to promote the gas blowing effect that controls the transfer amount and mixing degree of the fluidized medium. It is possible to adopt a configuration such as a thing.

The features of the present invention described above are mainly the following two points. a, The fluidized bed combustion furnace and the heat recovery cell were connected by a screw feeder, and the fluidized medium was transferred to the fluidized bed combustion furnace while being exposed to the low temperature outside air as much as possible. b, the outlet of the screw feeder was connected to a position lower than the fluidized air blowing position of the fluidized bed combustion furnace, that is, a position where the outlet of the screw feeder merges with the fluidized medium already cooled by the fluidized air.

As described above, the present invention has the following effects. a. By transferring the fluidized medium from the heat recovery cell to the fluidized bed combustion furnace at the shortest distance and without using a low-temperature carrier medium (compressed air etc.), the temperature drop of the fluidized medium is minimized, and heat loss and Reduced pulverization due to thermal shock. b, The medium in the bed of the fluidized bed combustion furnace is cooled by the fluidized air when passing through the diffuser tubes. Therefore, if the in-layer medium from the heat recovery cell is sent to a position lower than the position where the fluidized air is blown in, the thermal shock can be alleviated and the pulverization of the fluidized medium can be reduced.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention are shown in FIGS.
Shown in 1 is a system diagram of an embodiment according to the present invention, and FIG. 2 is a fluidized bed combustion furnace 6 and a heat recovery cell 23 according to the present invention.
2 is a side cross-sectional view of FIG. 3 taken along the line CC in FIG. 3, FIG.
-A line arrow view, FIG. 4 is a BB line arrow view of FIG.

Combustion air is blown into the fluidized bed 7 of the fluidized bed combustion furnace 6 from the header 4 through the air diffuser 5 through the pipe 3 through the air preheater 2 by the forced draft blower 1.
A fluidizing medium such as sand in the bed is fluidized.

The dust introduced into the fluidized bed combustion furnace 6 through the dust inlet 9 reacts with the air blown from the diffuser pipe 5 and burns to heat the fluidized medium, and most of it becomes combustion exhaust gas from the duct 10. After being discharged, it is exhausted through the chimney 16 by the induction blower 15 via the evaporator 11, the economizer 13, the air preheater 2, and the bag filter 14.

In the evaporator 11, the economizer 13, and the air preheater 2, since the fluid temperature in the heat transfer tube is low, corrosion can be suppressed within an allowable range. Non-combustible foreign matters such as metal pieces and pebbles are contained in the dust, and these cannot be fluidized and are deposited on the bottom of the fluidized bed combustion furnace 6. The fluidized medium is extracted from the bottom of the fluidized bed combustion furnace 6 through the extraction pipe 18 by the screw feeder 19 and sent to the sieve 20, where coarse incombustibles are separated and discharged to the outside of the system. The fluidized medium and the non-combustible foreign matter are cooled by the fluidized air blown out from the air diffusing tube 5 when passing between the air diffusing tubes 5.

The fine fluidized medium that has passed through the sieve 20 is returned to the fluidized bed combustion furnace 6 again by a bucket conveyor 22 or an air flow carrier pipe (not shown) to form a fluidized bed.

Heat recovery cell 23 installed in the fluidized bed combustion furnace 6
Air is blown through the air blower 1, the air preheater 2, and the pipe 24 through the air diffuser 25 (header 26) to control the internal fluidization state. By adjusting the amount of air, the heat recovery cell 23 can be controlled from the moving bed state to the fluidized bed state.

The lower part of the heat recovery cell 23 and the fluidized bed combustion furnace 6 are connected by a pipe 29 in which a screw feeder 28 rotated by a motor 27 is arranged, and a superheated steam pipe 30 (header 31) in the heat recovery cell 23. The fluidized medium which is deprived of heat and cooled is transferred into the fluidized bed combustion furnace 6 in the shortest distance.
An aeration nozzle 31 is provided in the fluidized bed combustion furnace 6 near the pipe 29 in which the screw feeder 28 is arranged,
Aeration air is blown into the screw feeder 2 through the push blower 1, the air preheater 2, and the pipe 32.
8 The transfer amount of the fluid medium from the heat recovery cell 23 into the fluidized bed combustion furnace 6 is secondarily increased by reducing the resistance of the outlet portion to facilitate the transfer of the fluid medium and increasing or decreasing the aeration air amount. Have control. Further, since this aeration air entrains the low-temperature fluid medium in the lower part of the air diffuser 5, it has the effect of lowering the average temperature when the heat recovery cell 23 and the in-layer medium of the fluidized bed combustion furnace 6 are mixed. It has the effect of relieving shock.

Further, a partition plate 33 is provided at a constant distance from the outlet of the screw feeder 28, and the partition plate 3
Aeration air is blown between the wall of the fluidized bed combustion furnace 6 and the wall of the fluidized bed combustion furnace 6 to generate an ascending flow of the fluidized medium in that portion by the air pump effect, thereby promoting mixing with the high temperature fluidized medium in the fluidized bed combustion furnace 8. There is.

As a result of transporting the fluidized medium to the fluidized bed combustion furnace 6 by the screw feeder 28, the heat recovery cell 2 lacking
The fluid medium in 3 is supplemented by the high temperature fluid medium overflowing from the fluidized bed combustion furnace 6 to the heat recovery cell 23 through the connecting pipe 34. This high-temperature fluidized medium comes into contact with the superheated steam pipe 30, gives heat to the superheated steam to lower the temperature, and is again sent to the high-temperature fluidized bed combustion furnace 6 by the screw feeder 28.

As described above, the high-temperature superheated steam pipe can be arranged while avoiding contact between the combustion exhaust gas of dust containing corrosive gas such as chlorine and the superheated steam pipe 30, whereby high-temperature high-pressure steam conditions can be obtained. In addition, the heat dissipation loss of the fluidized medium and the pulverization due to the thermal shock can be minimized.

According to the present invention, the fluid medium is smoothly transferred from the heat recovery cell 23 to the fluidized bed combustion furnace 6 by the screw feeder 28, and the flow in the fluidized bed combustion furnace 6 is provided with the partition plate 33 and the aeration nozzle 31. You can mix the media smoothly, but without using these,
It is possible to reduce the heat loss of the fluidized medium, to powder the fluidized medium due to thermal shock, and to reduce wear and tear.

The effects of the present invention are as follows. a. Since the heat loss when the fluidized medium is transferred from the heat recovery cell to the fluidized bed combustion furnace can be reduced, the thermal efficiency of the entire plant can be improved. b. It is possible to reduce the amount of pulverization and the amount of wear of the fluidized medium due to a thermal shock when the fluidized medium extracted from the heat recovery cell is returned to the fluidized bed combustion furnace. That is, since the new replenishment amount of the fluidized medium is small, the operating cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a system diagram of a fluidized bed combustion apparatus according to an embodiment of the present invention.

FIG. 2 is a side sectional view of the fluidized bed combustion furnace and heat recovery cell of FIG.

FIG. 3 is a view taken along the line AA of FIG.

4 is a view taken along the line BB of FIG.

FIG. 5 is a system diagram of a conventional fluidized bed combustion furnace with a heat recovery cell.

[Explanation of symbols]

1 forced blower 2 air preheater 3 piping 4 header 5 diffuser pipe 6 fluidized bed combustion furnace 7 fluidized bed 9 dust hole 10 duct 11 evaporator 13 economizer 14 bag filter 15 induced blower 16 chimney 18 extraction pipe 19 screw feeder 20 Fluui 22 Bucket Conveyor 23 Heat Recovery Cell 24 Piping 25 Diffuser Tube 27 Motor 28 Screw Feeder 29 Piping 30 Superheated Steam Pipe 31 Aeration Nozzle 32 Piping 33 Partition Plate 34 Connection Pipe

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiromichi Fujiwara 1-2-10 Isogo, Isogo-ku, Yokohama-shi, Kanagawa Babcock Hitachi Ltd. Yokohama Engineer Ring Center

Claims (10)

[Claims] 1. A fluidized bed combustion apparatus provided with a heat recovery cell provided with a fluidized bed combustion furnace in which fluidized air is blown into the fluidized medium, and a heat transfer tube for transferring the fluidized medium between the fluidized bed combustion furnace. A fluidized bed combustion apparatus characterized in that the fluidized medium from the upper part of the fluidized bed combustion furnace is extracted and put into a heat recovery cell, and the fluidized medium after heat exchange in the heat recovery cell is returned to the lower part of the fluidized bed combustion furnace. Driving method. 2. The method for operating a fluidized bed combustion apparatus according to claim 1, wherein the fluidized medium in the heat recovery cell is returned to the lower part of the fluidized bed combustion furnace by a screw feeder. 3. The fluidized medium from the heat recovery cell to the fluidized bed combustion furnace is returned to the same level as or lower than the fluidized air blowing position of the fluidized bed combustion furnace. A method for operating the fluidized bed combustion apparatus described. 4. The amount of fluid medium transferred from the heat recovery cell to the fluidized bed combustion furnace by blowing gas into the inside of the fluidized bed combustion furnace, which is the outlet of a screw feeder that connects the heat recovery cell and the fluidized bed combustion furnace. The method for operating a fluidized bed combustion apparatus according to claim 1, 2 or 3, wherein the fluidizing medium transferred from the heat recovery cell to the fluidized bed combustion furnace is promoted to be mixed while being controlled. 5. A partition is provided inside the fluidized bed combustion furnace, which is the outlet of the screw feeder connecting the heat recovery cell and the fluidized bed combustion furnace, to promote the gas blowing effect that controls the transfer amount and the mixing degree of the fluidized medium. 1, characterized by
The method for operating the fluidized bed combustion apparatus according to 2, 3, or 4. 6. A fluidized bed combustion apparatus provided with a heat recovery cell having a fluidized bed combustion furnace in which fluidized air is blown into the fluidized medium and a heat transfer tube for transferring the fluidized medium between the fluidized bed combustion furnace. An extraction pipe for extracting the fluid medium from the upper part of the fluidized bed combustion furnace to the upper part of the heat recovery cell was provided, and a return pipe for returning the fluidized medium after heat exchange was provided from the lower part of the heat recovery cell to the lower part of the fluidized bed combustion furnace. A fluidized bed combustion device characterized by the above. 7. The fluidized bed combustion apparatus according to claim 6, wherein the return pipe for returning the fluidized medium after heat exchange from the lower part of the heat recovery cell to the lower part of the fluidized bed combustion furnace is constituted by a screw feeder. . 8. The screw feeder connecting the heat recovery cell and the fluidized bed combustion furnace is connected at the outlet thereof at the same height as or lower than the fluidized air blowing position of the fluidized bed combustion furnace. Item 6. A fluidized bed combustion device according to item 6 or 7. 9. The flow according to claim 6, 7 or 8, wherein a gas injection pipe is provided inside the fluidized bed combustion furnace which is an outlet of a screw feeder connecting the heat recovery cell and the fluidized bed combustion furnace. Layer combustion device. 10. A partition plate is installed inside the fluidized bed combustion furnace, which is the outlet of the screw feeder connecting the heat recovery cell and the fluidized bed combustion furnace, for controlling the transfer amount of the fluidized medium and promoting mixing. The fluidized bed combustion apparatus according to claim 6, 7, 8 or 9.